The present invention resides in a roll dispenser capable of feeding sheet material out over a work surface, and deals more particularly with a brake for such a dispenser in which a means is provided for feeding out a discreet section of sheet material from a supply roll and stopping the supply roll with the advancement of the sheet material from the roll.
Conveyorized vacuum tables used for supporting a layup of the sheet material and advancing it to a work station where a work operation is performed on it, such as cutting, are well known. One such type of vacuum table is disclosed in U.S. Pat. No. 4,646,911, issued to David Pearl on Mar. 3, 1987. In this patent, it is disclosed that a conveyorized belt comprised of sections or slats of penetrable bristle surfaces which form a bed for supporting the sheet material and advancing the sheet material towards a final station may be employed for this purpose. A vacuum is provided which migrates longitudinally and laterally through the bristles thereby compressing and holding the sheet material in place on top of the conveyor for cutting by an automatically controlled cutting blade. To assist in the compaction of the sheet material which usually is several plies thick onto the work surface by the vacuum, it is often desirable to use a thin film of plastic which is drawn over the topmost ply of the layup. Often, the supply of sheet material and the associated section of film are drawn together across the work surface with the advancement of the conveyor belt. Alternatively, the roll of sheet material may itself be advanced across the work surface to effect covering of the underlying layup. Regardless of how the supply of sheet material is advanced, it has been found that the film of plastic or any other nonpermeable sheet material which may be chosen for this purpose often does not unwind from the supply roll in increments corresponding to the amount advanced. That is, the inertia generated by the roll as the film is being pulled off continues the rotation of the supply roll even after the advancement of the film. Additionally, it has been found that in unwinding from the supply roll, the film generates a static electric charge which, if not grounded, can adversely affect the functioning of sensors and other electrical components in the machine.
Accordingly, it is an object of the present invention to include as part of the supply roll support a means which allow the supply roll to rotate freely with the advancement of the sheet material from the supply roll but which stops the rotation of the supply roll when advancement of sheet material is complete such that the sheet material unwinds evenly in conjunction with its advancement.
Still a further object of the present invention is to provide a supply roll brake which is low cost and of highly durable construction so as to be capable of repeatedly being used without need of replacement or substantial adjustment.
Yet a further object of the present invention is to provide a feeding mechanism for a supply roll of the aforementioned type wherein the mechanism allows a supply roll to be readily replaced with a new roll of sheet material without significantly altering the machine itself.
Still a further object of the present invention is to provide a material handling system in which the sheet material which unwinds from the supply roll is of the type of in which a static charge generated as a result of unwinding is readily dissipated.
Further objects and advantages of the present invention will become apparent by the following disclosure and the appended claims.